You can tune down and/or change string gauges within sensible limits. A half step down works fine. The limitation on how low you can go before the intonation cr@ps out is most often the (plain) 3rd string - anything thicker than a 0.018" usually sounds horribly "plonky" at, or close to, concert pitch, but thinner ones can become too floppy (and difficult to intonate) when tuned down - and again, using a wound 3rd is not an option if you have a True Temperament neck designed for a plain 3rd string.
Its off the website, check the FAQ section. Hope that helps :)